We installed a 2000 Watt Prosine 2.0 inverter charger that is capable of driving most 110V household tools and equipment like the microwave and even the air conditioner, although we seldom used it for that due to the high draw on the batteries.

As a very rough rule of thumb, 10 Amps at 110 Volts out of the inverter will draw about 100 Amps from the 12 Volt batteries.

This is a very smart inverter charger. The shorepower runs through the Prosine and it will switch automatically, without a glitch from shorepower to inverter if the power fails and back again when shore power is restored.

It also has a built in, multi-stage battery charger, capable of charging the battery bank from shore power at 105 Amps.

The battery charger is also very smart and can be programmed for the type of battery (AGM/Flooded/gel, etc) and charge the batteries in preprogrammed stages such as Bulk, Absorption and Float and it can also be programmed to do an equalization charge, from time to time, which is recommended by manufactureres of lead-acid batteries. During equalization, the current is capped at 16 amps and the battery voltage is allowed to climb to as high as 18 Volts to overcharge the cells, get rid of sulfates and equalize the charge in each cell. I normally remove the battery caps and monitor the fluid level during this process.

Low current requirements

We also had a small 150W inverter for running a laptop or 110V flourescent light. We found this more efficient than firing up the big 2000W inverter, which draws a little overhead current even when sitting idle.Howard [ Just Imagine ] 01-Jan-2008

Although there are a few marinas that have strange shore power connectors that you need to buy or rent from them, most are fairly standard throughout the Mediterranean. These are 240V 16A 3 Pin connectors (see picture) that are available in just about any hardware store or chandler, in almost any port, for a few Euros.

We bought ours in a hardware store in Horta, Azores. We also bought 25 meters of 25mm2 (14 AWG) 3 conductor wire.

On the boat side, we connected a standard, European household type (2 pin + ground), 240V female socket which connected, in turn, to the 240V/120V step down transformer.

I don't like to leave shore power connected to the boat when I am not onboard, so we simply ran the cable down the companionway to the transformer which sat below the companionway steps. This way I am reminded when I leave and lock up the boat to disconnect the cord. A more professional approach would be to have a deck connector that is permanently wired to the transformer.

Some marinas have 32 Amp power outlets which look like overgrown versions of the 16 Amp connectors and only cost a little more. We made up a short adapter cable with a male 32 Amp plug and a female 16 Amp socket. It might be a good idea to split the 32 Amp plug into two 16 amp sockets.

Another adapter cable that we made up was a 16 Amp male to two 16 Amp females. This is useful, when you get to the dock and find all of the receptacles are occupied by other boats. You then simply unplug the neighbour (preferably after asking permission) and plug him and yourself into your double adapter cable to share the plug.

You may want to keep some extra 16 Amp plugs and sockets and wire onboard so that you can make up new adapters as the situation demands.

Shore power voltages vary considerably, depending on the quality of the marina wiring, the distance from the source and the number of boats drawing power on the same line. It is not uncommon to see voltages below 200 volts which can sometimes upset some equipment on board.Howard and Jayne [ Just Imagine ] 28-Jan-2008

There are several ways to deal with 240 Volt power on a 110 Volt boat. The simplest is to buy a 220 Volt battery charger to charge your 12 Volt batteries, and draw your 110V from your inverter as usual.

The best solution is a 240V/120V step down isolation transformer. This isolates the boat electrically from the shore power and helps to reduce spikes in the power.

The disadvantage of an isolation transformer with primary and secondary windings is the physical size, weight and cost needed to provide 3000-5000 VA depending on your current requirements.

On Just Imagine, we used a small 3000VA autotransformer which is much lighter at about 40 lbs (20Kg) and only cost about $150. The auto transformer only uses a primary winding which is center tapped to feed off 120 Volts.(see diagram below).

The disadvantage of this is that the power on the boat is not electrically separated from the shore power. The dock power outlet wiring can vary from marina to marina. When connecting shore power to the transformer, you need to measure the voltage between the neutral and ground on the output of the transformer before connecting to the boat. This should be zero, or just a few volts. With the 2 prong connector, you have a 50/50 chance of getting it wrong when you will have 220V between neutral and ground. To correct this you simply need to remove and reverse the 2 pin (+ ground) plug on the input to the transformer, and then measure your voltages again.

On Just Imagine, the transformer went to the Prosine 2.0 Inverter charger, and then to the electrical panel on the boat. The Prosine would go into an alarm condition if I got it wrong, but I preferred to measure with a volt meter before connecting to the boat.